The present invention relates to wafer support apparatus in semiconductor fabrication device and, more particularly, to means for vertically moving a wafer, provided in wafer support apparatus.
There is semiconductor fabrication device of a single wafer type for processing a single silicon wafer at a time. In the semiconductor fabrication device of this single wafer type, a wafer support apparatus for supporting only one wafer in a horizontal posture is normally provided in a process chamber.
The ordinary wafer support apparatus is basically constructed of a wafer support body, so called a susceptor, on which a wafer is mounted. The wafer support apparatus is also provided with a lift mechanism for vertically moving the wafer relative to the susceptor. A conventional, ordinary lift mechanism has a plurality of lift pins extending through the susceptor and a wafer is mounted on the upper ends of these lift pins. Thus the wafer can be moved up and down by vertically moving the lift pins. The lift mechanism of this type permits a wafer carried on a blade of a carry robot to be transferred onto the susceptor or, inversely, it permits the wafer to be brought from the susceptor to the carry robot.
In the conventional wafer support apparatus as described above, the lift pins are located at the position below the upper surface of the susceptor during supporting periods of wafer. Therefore, when the lift pins are moved up in order to lift the wafer from the susceptor, the upper ends of the lift pins hit the back surface of the wafer and sometimes damage the contact portions. Such damage on the back surface of wafer might cause a negative effect in postprocesses.
In addition, since the back surface of the wafer is supported by only the upper ends of the lift pins during vertical motion of the wafer, the wafer readily undergoes positional deviation and can deviate from the support area of the susceptor when brought down onto the susceptor.
The present invention has been accomplished under such circumstances and an object of the present invention is to provide wafer support apparatus having a lift mechanism capable of preventing the damage of the back surface of the wafer and the positional deviation of the wafer.
In order to accomplish the above object, the present invention provides a wafer support apparatus comprising a wafer support body having a support area for supporting a wafer, in an upper surface thereof; and a plurality of lift members, each extending from the outside to the inside of the support area of the wafer support body, having a slope surface sloping downward toward the inside, in an upper surface, and being vertically movable between a lower position and an upper position with respect to the upper surface of the wafer support body.
The lift members replace the conventional lift pins. They do not touch the back surface of the wafer but touch only the lower edge in the periphery of the wafer, because of the setting positions of the lift members and the slope surfaces of the upper surfaces thereof. Therefore, the back surface of wafer can be prevented from being damaged. Since the upper surfaces of the lift members increase their height with distance from the center, it is also feasible to suppress the positional deviation in the horizontal direction.
The lift members are preferably formed integrally with an internal peripheral edge of a lift ring of an arcuate shape disposed outside the support area.
In an effective configuration, the lift ring is provided with claw members kept in a vertically movable state and at respective positions adjacent to the lift members and the claw members are arranged to be separated and lifted from the lift ring when the lift ring is located at an up position. In this configuration, the claw members located at the position higher than the wafer can prevent the wafer supported by the lift members, from moving horizontally.
Further, a cross-sectional shape of the upper surfaces of the lift members along the circumferential direction of the support area is preferably an upwardly convex curve. This permits the lift members to be brought into point contact with the wafer.